AbstractBackgroundStrategies for breast cancer prevention are informed by assessing whether incidence differs by tumour biology. We describe temporal trends of breast cancer incidence by molecular subtypes in Scotland.MethodsPopulation-based cancer registry data on 72,217 women diagnosed with incident primary breast cancer from 1997 to 2016 were analysed. Age-standardised rates (ASR) and age-specific incidence were estimated by tumour subtype after imputing the 8% of missing oestrogen receptor (ER) status. Joinpoint regression and age- period- cohort models were used to assess whether significant differences were observed in incidence trends by ER status.ResultsER positive tumour incidence steadily increased particularly for women of screening age 50 to 69 years from 1997 till around 2011 (1.6%/year, 95%CI: 1.2 to 2.1). ER negative incidence decreased among all ages at a consistent rate of −0.7%/year (95%CI: −1.5, 0) from around 2000-2016. Compared to the 1941-1959 central birth cohort, women born 1912-1940 had lower incidence rate ratios (IRR) for ER+ tumours and women born 1960- 1986 had higher IRR for ER- tumours.ConclusionsWe show evidence of aetiologic heterogeneity of breast cancer. Future incidence and survival reporting should be monitored by molecular subtypes.
Distinct temporal trends in breast cancer incidence from 1997 to 2016 by molecular subtypes: a population-based study of Scottish cancer registry data
